Apparatus for converting direct current into periodic varying current



fiat. 7 1941. K. H. SCHMIDT ETAL 2,258,3Q3

APPARATUS FOR CONVERTING DIRECT CURRENT INTO PERIODIC VARYING CURRENTFiled July 20, 1938 2 Sheets-Sheet 1 WM/flNTGRfi KARL, HERF MNNSCHMHD'EMARPUE "WAKOMNCH ATTGRNEVS (kt 7, 1941. K. H. scHMmT ETAL 2,253,393

APPARATUS FOR CONVERTING DIRECT CURRENT INTO PERIODIC VARYING CURRENTFiled July 20, 1958 2 Sheets-Sheet 2 a wwimmm: mm E fiERM/WN swmm" MARWSWE mmwmw enema on. 1, 1941 immune roa comamo n'mso'r cnanam' m'rorsaromc vaamo ounm1 Hermann Schmidt, London, England, and

Marina Widakowich, Vienna, Ge

many; said- Widakowlch assiznor tosaid Schmidt Application July 20,1938; Serial No. 220,116

In Austria July 29, 1937 I GCIaims.

This invention relates to apparatus for converting direct current intoperiodic variable current and is concerned with apparatus which mayproduce an alternating current or generally a cyclic current that may bepulsatingdirect current.

Up to the present, mechanical transiormers having oscillating orrotating contacts have been little used in practice due to the fact thatif large currents are being passed between the contacts there is rapidwear caused by arcing and the like. a

It is one of the chief objects of the invention to devise apparatuswhich will permit the use of contact devices whilsti'substantiallyavoiding the difficulties hitherto experienced therewith.

Following the principles ofmthe invention a condenser is arranged forcharging from the directcurrent source and the charging of the condenseris continued until the charging current reaches a low point, where thecircuit is broken and, if desired, a discharge of the condenser throughan auxiliary circuit is permitted. In this way the break of the circuittakes place at a point where only low currents are concerned. Ifdesired, instead of allowing the condenser to discharge through anauxiliary circuit it may be connected back to the direct current sourcein such manner that it is charged in an opposite direction whereby thefull value of the condenser is more nearly utilised.

Hereinafter, and in the claims that are a pended hereto, the expressionthe condenser is to be read as covering a single condenser or a groupthereof arranged in any desired manner.

In order that the said invention may be clearly understood and readilycarried into efiect, the same will now be more fully described withreference to the accompanying drawings, in which:

Figures 1 to 4 are diagrammatic illustrations of how electricalapparatus embodying the invention may be connected and arranged, and

Figures 5 and 6 are respectively side and end views of a constructionaldetail of the apparatus forming the subject of the invention.

Referring first to Figure l of the drawings it will be seen that thereis a condenser l and a source of direct current 2. One side of thecurrent source 2 is shown connected with one of a pair of terminals 4,the other of which is connected to one side of the condenser l. Theother side of the condenser connects with a leaf 3 which serves as acontactor and which also carbe influenced by electr c-magnetic winding 3having a core 8, the winding 6 being connected to the other side of thesource of direct cur-f lrent 2. There is a contact-piece I connectedwith the coil [and adaptedto be engaged by the leaf 3. A parallelconnection I is made across the condenser l and includes a winding 9similar to that indicated at 5 and likewise possessing a core I0. Thereis also a contact ll disposed in like manner to the contact I.

The terminals 4 are connected by an outputelement I2 or by an outputelement IZA. The

output element l2, as will be seen from the drawings, has but twoterminalswhich bridge across the terminals 4 whereas with the outputelement illustrated at I2A, there is a pair of input terminals. l3 and apair of output terminals 14, the terminals l3 being for connection tothe terminals 4. These output elements may be of any desired form, andmay in certain instancesrepresent the load that is to be supplied withthe periodic varying current. The output elements may include merelyohmic resistance or may include a combination of ohmic resistance,inductance or capacitance.

With the apparatus so far described in operation, the leaf 3 carry ngthe armature 4A may contact with either of the contacts I or II. If itis supposed that it is contacting with the contact member I, it will beobserved that a circuit is completed from the source of direct current2, through the output element H or 12A, to the condenser i from whencethere is a return through the leaf 5 itself and the winding 5 to thesource of electro-motive force 2. Under these circumstances, thecondenser i will charge and, in known manner, when the condenser isreaching full charge the current flowing in the charging circuit will begradually reduced. The leaf 3 will be held in contact with the contactmemher 1 for the reason that the current flowing in the charging circuitwill also flow through the coil 5, and the armature 4A will be attractedto the core 6. In a manner which will be explained hereinafter a springX is arranged to urge the armature 4A away from the core 6, so that asthe current in the charging circuit decreases there will be a pointwhere the spring just referred to will cause the armature 4A to moveaway from the core 6 and thereby to break-the charging circuit. The leaf3 then moves over to an opposite position against the action of a springY where a circuit is completed through the condenser l, the parallelconnection 8 and the coil 9,

rice an armature 4A. The latter is arranged to for the reason thatthe'leaf 3 will contact with the contact member II. As soon as thiscircuit is completed, the condenser I will cause a surge of current toflow through the closed parallel circuit, andsuch current will continueto flow until the condenser is substantially discharged when the forceof attraction exerted on the armature 4A by the core in of the coil 9will fall below a predetermined magnitude. The spring Y is arranged inthe same manner as the spring IX, so that the leaf will be carried backto its opposite working position with consequent breaking of the circuitthrough the previously closed parallel circuit when the current thereinhas fallen below said predetermined value. The initial operation of thedescribed device may be effected by hand.

The circuit arrangement described above may be modified in certainrespects and, in particular, if desired, a current consumer may beincluded in the parallel circuit or in the common part of the circuitassociated with the condenser I itself. Similarly, the electro-magneticholding means for the armature 4A might be included in the part of thecircuit containing the condenser I so as to obviate the necessity fortwo separate electro-magnetic holding means. In Figure 2 of the drawingsa circuit similar 'to Figure 1 is shown except that both modificationsjust indicated have been made. The output element I2 is shown located inthe common branch of the circuit so that it now experiences the flow ofcurrent in both directions, and similarly the electro-magnetic coil I5with associated core I6 is located in the common branch.

The core I6 will have its polarity changed with each alternation of thecurrent in the common branch, and thus the armature 4A will take up itsalternate positions to cause the desired alternate closing of the twocircuits offered. The arrangement is otherwise the same as thatdescribed in connection with Figure 1.

In the arrangement according to Figures 1 and 2, it will be observedthat the condenser I is first charged and then allowed to dischargethrough the auxiliary parallel circuit. In Figure 3 the arrangement issuch that the condenser I is first charged in one direction and is thencharged in the opposite direction, whereby the condenser is used togreater advantage. In the circuit arrangement of Figure 3, there is, asbefore, a source of direct current 2 and output terminals 4. There is alead I 1 from one side of the current source 2 connecting with a coil I8associated with a core I9 and a contact member 20. There is a branchconnection 2I joining one end of a further coil 22 likewise associatedwith a core 23 and a contact member 24. There is a connection 25 fromthe other side of the current source 2, to a double-pole contact member26. There is, in this case, a pair of leaves 21 and an associatedarmature 28, the armature 28 being arranged so as to be influenced byeither the core I9 or the core 23, according to whether the winding I8or the winding 22 is excited. One of the leaves 21 is joined by aconnection 28 which extends to one of the terminals 4. The other of theleaves 21 is joined by a connection 30 through the condenser I to theother of the output terminals 4. The output terminals 4 may beassociated with an output element I2 or I2A, as already described. Theleaves 21 and the associated armature 28 are spring-loaded in the samemanner as described with reference to Figures 1 and 2, that is to say,in such manner that when the leaves 21 are brought to a position whereone contacts with, say, the contact member 24 and the other with thedouble-pole contact member 23, there is a resilient spring pressuretending to return the leaves 21 with the associated armature 28, to theopposite position where one leaf contacts with the contact member 2|,and the other with the opposite contact of the contact member 28. Thespring pressure thus tends always to displace the leaves and armature tothe opposite working position from that in which they may be. for thetime being, situated. However, such spring pressure cannot assert itselfuntil the current flow through the associated holding electro-magnet hasfallen below a predetermined minimum.

In operation the arrangement of Figure 3 is such as to charge thecondenser I first in the one direction, and then to charge it in theopposite direction and so on continuously, the leaves 21 oscillatingbetween their extreme working positions. The outflow obtained betweenthe terminals 4 will, in this instance, be alternating. When theconverter apparatus is on light-load or is merely idling it ispreferable that the output terminals 4 should be bridged in order toprevent the stopping of the mechanical oscillations of the leaves 21. InFigure 3, there is indicated in dotted lines at 3| a condenser which maybe connected in parallel between the connections 29 and 30 for thepurpose of maintaining the mechanical oscillation of the said leaves. Aswitch 3IA allows the condenser 3| to be brought optionally intooperation.

In Figure 4 an arrangement similar to that of Figure 3 is shown, withthe distinction that in this case the two electro-magnetic devicesconsisting of the windings I8 and 22, and associated cores I9 and 23,are replaced by a single winding 32 which is located in a common branchof the circuit including the condenser I. The arrangement otherwisecorresponds to Figure B'in the same way that Figure 2 corresponds toFigure 1. The winding 32 has a core 33 adapted to cooperate with thearmature 28.

In Figures 5 and 6 of the drawings, there is shown a constructional formof the electro-magnetic device together with vibrator leaves andarmature therefor. In the illustrated embodiment, the vibrator leavescorresponding to those indicated at 21 in Figure 3 are shown at 34 and35. They are supported in a block 36 of insulating material and mayoscillate between extreme working positions defined by pairs of stops 31and 38, (only one of each pair shown in Figure 5). There are pairs ofcontact elements 38 and 40 secured to each of the stops.

At the upper end, the leaves 35 and 34 support the armature H. AnE-shaped core 42 carries a winding 43 which may correspond to thewinding 32 shown in Figure 4. The lower ends of the spring leaves 34 and35 are pivotally secured as at 44 in the block 36.

It will be understood that when a pulsating direct current or analternating current is being passed through the winding 43 the core Uwill oscillate and will cause the leaves 34 and 35 to be flexed. As theamplitude increases the leaves will be bent back over the contacts 39and 40, which contacts are shaped as will be seen in Figure 5, so as topermit the leaves to bend over them.

It will be understood that the armature 4I might be replaced by one ofthe polarised type. Furthermore, each leg of the E-shaped core 42 mightcarry a winding; for example the two outside legs might have windingsplaced thereon adapted to conduct a pulsating direct current, or theinnermost leg of the core might have a winding conducting only analternating current. as shown in the drawings, or the dispositions ofthe windings mentioned might be entirely reversed. The dotted lines inFigure indicate the limit working positions of the springleaves.

In those constructions described above where flexlon springs areemployed, as in Figures 5 and 6, to store mechanical energy it is notnecessary that the fiexionsprings should be arranged exactly asindicated in Figures 5' and 6. Thus, the stationary contacts indicatedat 39 and I may be replaced by springs, Also the surface contactsindicated may be replaced by pointed contacts. The arrangement may besuch that the mechanical resonance of the vibratory system is not suchas to influence greatly the electrical resonance point of the describedsystems. Where such mechanical resonance does not predominate to anymarked extent, it will be observed that the frequency or the amplitudeof the pulsating or alternating current given as the output from theapparatus of the invention, will depend upon the voltage oi the directcurrent source, since the rate of charging of the condenser will dependupon such voltage.

What we claim and desire to secure by Letters Patent of the UnitedStates is:

1. Apparatus for converting direct current into periodic varyingcurrent, comprising a condenser arranged in a circuit including a directcurrent source, a circuit breaker located in the circuit of thecondenser, an electro-magnetic device controlled by the current in thecondenser circuit and arranged to hold the circuit breaker closed whencurrent above a predetermined minimum is flowing through *saidelectro-magnetic device, means associated with said circuit breaker andarranged to be held in tension whilst current above said minimum isflowing and for bringing said circuit breaker into an open positionafter the current has fallen below said minimum and at least one currentconsumer located in the condenser circuit.

2. Apparatus for converting direct current into periodic varyingcurrent, comprising a first circuit, a condenser, a direct currentsource and a switch device all located in said circuit, a second circuitincluding said condenser and being closable through said switch device,means for normally maintaining said switch device in an operativeposition where it completes neither circult, an electro-magnetic meansfor operating said switch device so that said first and second circuitsare alternately closed, each circuit being maintained closed until thecurrent therein falls below a predetermined minimum, and at least onecurrent consumer located in circuit with the condenser.

3. Apparatus for converting direct current into periodic varyingcurrent, comprising a first circuit, a source of direct current, acondenser and a switch device, all located in said circuit, a secondcircuit consisting of a parallel connection across the condenserandjoined to said switch device, an operative member in said switchdevice for closing either said first circuit or said second circuit,electro-magnetic means for controlling said operative member of theswitch device so that the latter may alternately close either of saidcircuits maintaining the circuits closed until the current therein fallsbelow a predetermined minimum, means for influencing said operativemember of the switch to cause the latter always to tend to occupy anopposite working position from that which it may, for the time being, heoccupying, and at least one current consumer located in circuit with thecondenser.

4. Apparatus for converting direct current into periodic varyingcurrent, comprising a first circuit including a source of D. 0. supply,a second circuit parallel across thesource of D. C. supply, a changeoverswitch device, a condenser connected to the common poles of saidchangeover switch device, connections in both said first and secondcircuits to the fixed poles of the changeover switch device to permiteither said first or second circuit to be completed through saidcondenser, electro-magnetic means for holding the changeover switchdevice in either extreme working position, said electro-magnetic meansbeing controlled according to the current in said first and secondcircuit, so that when said current falls below a predetermined minimum,the changeover switch device assumes an opposite working position underthe action of said electro-magnetic device, and at least one currentconsumer in circuit with the condenser.

5. Apparatus for converting direct current into periodic varyingcurrent, comprising a condenser arranged in a circuit including a directcurrent source, a circuit breaker device located in the circuit or thecondenser, an electro-magnetic device controlled by the current in thecondenser circuit, an armature secured to the operative member in saidcircuit breaker device and located adjacent said electro-magnetic deviceto after the current has fallen below said minimum and at least onecurrent consumer located in the condenser circuit.

6. Apparatus for converting dh'ect current into periodic varyingcurrent, comprising a condenser arranged in a circuit including a directcurrent source, a fixed contact located in said circuit, at leastonevibrator leaf connected in said circuit and arranged to co-operatewith said fixed contact, an armature carried by said vibrator leaf,electro-magnetic means controlled by the current in the condensercircuit and arranged to hold said armature in a position where thevibrator leaf co-operates with said fixed contact to close the saidcircuit when current above a predetermined minimum is flowing throughsaid electro-magnetic means, and a current consumer located in thecondenser circuit.

KARL HERMANN SCH'MUD'I. MARIUS WIDAKOWICH.

